The overall objective of these studies is to understand the structure and function of membrane-bound bovine enterokinase and to relate these properties to other serine proteinases. Most of the investigation will focus on the amino acid sequence determination of the light chain (the catalytic chain) of the enzyme. The sequence analysis will be performed with a solid-state methodology and a strategy that utilizes minimal amounts of protein will be followed. A selective reduction of the disulfide bonds linking the heavy and light chains will be performed under conditions which maintain the globular structures of the chains. The catalytic properties of the isolated light chain will be studied and the heavy chain will be tested for regulatory properties. Enterokinase will be embedded in synthetic phospholipid vesicles and the properties of the membrane-bound enzyme will be examined.